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Message-Id: <20200618032125.4650-2-zhenzhong.duan@gmail.com>
Date: Thu, 18 Jun 2020 11:21:25 +0800
From: Zhenzhong Duan <zhenzhong.duan@...il.com>
To: linux-kernel@...r.kernel.org
Cc: linux-spi@...r.kernel.org, broonie@...nel.org,
Zhenzhong Duan <zhenzhong.duan@...il.com>
Subject: [PATCH 2/2] spi: spidev: fix a potential use-after-free in spidev_release()
If an spi device is unbounded from the driver before the release
process, there will be an NULL pointer reference when it's
referenced in spi_slave_abort().
Fix it by checking it's already freed before reference.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...il.com>
---
drivers/spi/spidev.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index f74ea26..59e0767 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -609,15 +609,20 @@ static int spidev_open(struct inode *inode, struct file *filp)
static int spidev_release(struct inode *inode, struct file *filp)
{
struct spidev_data *spidev;
+ int dofree;
mutex_lock(&device_list_lock);
spidev = filp->private_data;
filp->private_data = NULL;
+ spin_lock_irq(&spidev->spi_lock);
+ /* ... after we unbound from the underlying device? */
+ dofree = (spidev->spi == NULL);
+ spin_unlock_irq(&spidev->spi_lock);
+
/* last close? */
spidev->users--;
if (!spidev->users) {
- int dofree;
kfree(spidev->tx_buffer);
spidev->tx_buffer = NULL;
@@ -625,19 +630,14 @@ static int spidev_release(struct inode *inode, struct file *filp)
kfree(spidev->rx_buffer);
spidev->rx_buffer = NULL;
- spin_lock_irq(&spidev->spi_lock);
- if (spidev->spi)
- spidev->speed_hz = spidev->spi->max_speed_hz;
-
- /* ... after we unbound from the underlying device? */
- dofree = (spidev->spi == NULL);
- spin_unlock_irq(&spidev->spi_lock);
-
if (dofree)
kfree(spidev);
+ else
+ spidev->speed_hz = spidev->spi->max_speed_hz;
}
#ifdef CONFIG_SPI_SLAVE
- spi_slave_abort(spidev->spi);
+ if (!dofree)
+ spi_slave_abort(spidev->spi);
#endif
mutex_unlock(&device_list_lock);
--
1.8.3.1
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